This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective: To test the efficacy of a potential microbicidal agent to prevent transmission of HIV to women. Such an effective agent is urgently needed to combat the predominant rise globally of new HIV infections in women. This proposal tested in vivo the efficacy of glycerol monolaurate to prevent intravaginal transmission of simian immunodeficiency virus to rhesus macaques, a highly relevant nonhuman primate model of sexual mucosal transmission of HIV. We found that glycerol monolaurate does not alter rhesus macaque (Macaca mulatta) vaginallactobacilli and is safe for chronic use.